In LTE (Long Term Evolution) Release-10, CA (Carrier Aggregation) was introduced to realize wide-band communication beyond 20 MHz (for example, communication at 100 Hz). In CA, communication is performed by using bundled CCs (Component Carriers) under a single radio base station eNB as illustrated in FIG. 8(a).
Afterwards, in LTE Release-12 and beyond, “Small Cell enhancement” was proposed, and “Inter-site CA” in which communication is performed by using bundled CCs (cells) under different radio base stations eNB has been studied for introduction as a more flexible network architecture than conventional ones (see FIG. 8(b)).